You do not have "fog" lights at all with the RS.....only DRL's.
From the factory they go off when the headlights are on.
You can turn them off during the day by turning your headlight knob one turn to the left, but there is no switch to turn them on at night.
You can buy an aftermarket DIY wiring harness and replace the DRL's with fog lamps, which you could turn on and off anytime.